Receptors and Neurons Flashcards
sensory neuron
sends nerve impulses from receptors to cns
relay neuron
sends nerve impulses from sensory to motor neuron
motor neuron
send nerve impulses from cns to effectors
chain reaction from a stimulus to effectors
stimulus, receptors, via sensory neuron to the cns, via motor neurone to effectors, response
sensory receptors
act as transducers, convert energy of a stimulus into electrical energy
potential difference at rest
resting potential
what does a stimulus do to a receptor
excites the cell membrane, increases permeability, more ions move in and out.
change in potential difference due to a stimulus
generator potential
how to trigger an action potential
generator potential needs to reach the threshold level
pacinian corpus
mechanoreceptor that detects mechanical stimuli like touch, found in the skin and contain a sensory nerve ending
what is a sensory nerve ending wrapped in
lamellae
stimulating a pacinian corpus
e.g tap on arm. lamellae get deformed and press on sensory nerve ending, this causes a deformation of stretch mediated sodium channels, they open Na+ ions diffuse in, if GP reaches threshold action potential is triggered
structure of sensory neuron
many short dendrites that carry a nerve impulse from receptors to cell body via one long dendron, then this nerve impulse travels to cns via short axon
structure of motor neuron
many short dendrites that carry nerve impulses from cns to cell body, 1 long axon carries from cell body to effectors
structure of relay neuron
short dendrites carry nerve impulses from sensory neuron to cell body and one axon to the motor neuron
what happens at a neurones resting state in terms of charge
outside of membrane is more + charged than inside , membrane is polarised
what is the resting potential (number)
-70mV
how is the resting potential of a neurone maintained
na/k pumps move 3 Na+ ions out and brings in 2 K+ ions in (active transport). membrane impermeable to Na+ but some K+ ions diffuse out of cell via facilitated diffusion
1) Action potentials: Stimulus
stimulus excites cell membrane, becomes more permeable Na+ diffuses in via channels
2) Action potentials: Depolarisation
if PD reaches -55mV, voltage gated Na+ channels open so more Na+ enters the neurone this is POSITIVE FEEDBACK
3) Action potentials: Repolarisation
PD reaches +30mV this causes Na+ channels to close and voltage K+ channels to open and diffuse OUT, resting potential is maintained
4) Action Potentials: Hyperpolarisation
K+ channels are slow to close this causes an ‘overshoot”. PD becomes more negative than -70mV, Na/K pumps restore resting potential
Refractory Period
After an action potential, ion channels are recovering and can’t be opened.
How does a wave of depolarisation occur
when Na+ diffuses out sometimes they diffuse sideways this causes the Na channels in the next region to open and this process repeats.
effect of a bigger stimulus
more frequent action potentials
Myelinated neurones
have a myelin sheath which is made from Schwann cells, they are electrical insulators
Nodes of Ranvier
bare membrane, Na channels concentrated here, depolarisation in myelinated neurones occurs here, impulse jumps from node 2 node - salatory conduction
myelinated vs non myelinated
myelinated is faster
